Advanced functions have been recently installed into vehicles. The vehicles include various rotation angle detectors for detecting rotation angles of steering wheels to control various functions of the vehicle according to the detected rotation angles.
FIG. 6 is an exploded perspective view of conventional rotation angle detector 10. Flat gear 1A is provided on a side surface of rotor 1. Through-hole 1D is formed in the center of rotor 1, and engaging parts 1B and 1C protrude from an inner circumference of through-hole 1D.
Flat gear 2A is provided on an outer circumference of first detecting body 2. Flat gear 3A is provided on an outer circumference of second detecting body 3. Flat gear 3A has a different number of teeth than flat gear 2A. Flat gear 2A of first detecting body 2 is engaged with flat gear 1A of rotor 1. Flat gear 3A of second detecting body 3 is engaged with flat gear 2A of detecting body 2.
Wiring board 4 is located substantially in parallel with first detecting body 2 and second detecting body 3. Wiring patterns are provided on both surfaces of the board. Magnetic sensors 5B and 6B are mounted onto wiring board 4. Magnet 5A is attached to the center of first detecting body 2, and magnet 6A is attached to the center of second detecting body 3. Magnetic sensors 5B and 6B face magnets 5A and 6A, respectively.
Magnet 5A and magnetic sensor 5B facing each other constitute first detecting unit 105, and magnet 6A and magnetic sensor 6B facing each other constitute second detecting unit 106. A microprocessor and other electronic components mounted on wiring board 4 constitute controller 7.
Case 8 has substantially a box shape and is made of insulating resin. Cover 9 is made of insulating resin. Rotor 1, first detecting body 2 and second detecting body 3 are held rotatably in case 8. Wiring board 4 is fixed to the case. Rotor 1, detecting bodies 2 and 3, and wiring board 4 are accommodated in cover 9. Case 8 has through-hole 8A provided therein. Cover 9 has through-hole 9A provided therein. A steering shaft is inserted into through-holes 8A and 9A.
The centers of through-holes 8A and 9A agrees with a rotation axis of rotor 1. Case 8 has round hole 8B and elongate hole 8C provided therein at positions symmetrical to each other with reference to the rotation axis of rotor1.
FIG. 7 is an exploded perspective view of a vehicle having conventional rotation angle detector 10 installed therein. Rotation angle detector 10 detects a rotation angle of steering wheel 11, an object to be detected. Rotation angle detector 10 is arranged behind steering wheel 11 and mounted to a vehicle. Controller 7 is connected to an electronic circuit of the vehicle via a connector and a wire.
Rotary coupler 12 includes fixed housing 13 fixed to the vehicle, and rotatable housing 14 attached to fixed housing 13 rotatably with reference to fixed housing 13. A flexible cable is wound and contained in fixed housing 13. Rotatable housing 14 has through-hole 14A provided therein. An inner circumference of through-hole 14A is engaged with steering shaft 15.
FIGS. 8A and 8B are plan views of a conventional rotation angle detector. 10. Cutouts 14B and 14C formed in rotatable housing 14 are engaged with engaging parts 1B and 1C, respectively. Pins 13B and 13C having columnar shapes are provide on fixed housing 13 and inserted into round hole 8B and elongate hole 8C, respectively. Thereby, rotation angle detector 10 is held to rotary coupler 12 fixed to the vehicle.
Steering wheel 11 is rotated, and rotatable housing 14 engaged with steering shaft 15 rotates accordingly. Rotor 1 having engaging parts 1B and 1C engaging cutouts 14B and 14C of housing 14 rotates according to the rotation of rotatable housing 14.
Rotor 1 rotates, and first detecting body 2 rotates accordingly. Second detecting body 3 rotates according to the rotation of first detecting body 2. Magnets 5A and 6A attached to the centers of detecting bodies 2 and 3 rotate accordingly. The rotations of magnets 5A and 6A change magnetic fields from magnets 5A and 6A applied to magnetic sensors 5B and 6B. Magnetic sensors 5B and 6B detect the change of the magnetic fields as detection signals. First detecting body 2 and second detecting body 3 have different numbers of teeth and rotate at different rotation speeds, hence causing magnetic sensors 5B and 6B to output the signals having different cycles and different phases.
Controller 7 detects a rotation angle of rotor 1, i.e., a rotation angle of steering wheel 11, the object to be detected, based on the detection signals output from first detecting body 2 and detecting body 3 and the number of teeth of each of first detecting body 2 and second detecting body 3. Controller 7 outputs the detected rotation angle to the electronic circuit of the vehicle to perform various controls for controlling the vehicle.
Components, such as case 8, rotor 1, rotatable housing 14, and fixed housing 13, of rotary coupler 12 and rotation angle detector 10 are generally made of insulating resin, and hence, thermally expand and contract at high temperatures and low temperatures. Since having different sizes and being made of different materials, the components have different dimensional changes due to the thermal expansion and contraction, thereby causing a displacement between the components.
Rotation angle detector 10 and rotary coupler 12 have sizes larger than other components, accordingly having large dimensional changes due to the thermal expansion and contraction. In order to reduce the displacement due to the large dimensional changes, pin 13B having the columnar shape is inserted into round hole 8B, and pin 13C is inserted into elongate hole 8C. When case 8 expands in a direction D101 to the right, as shown in FIG. 8B, pin 13C moves in elongate hole 8C and absorbs the dimensional changes caused by the expansion, thereby preventing rotation angle detector 10 from malfunction due to warping or other deformation of the components.
Regarding the connection between rotor 1 and rotatable housing 14, however, gap L101 may be produced between engaging part 1C and cutout 14C due to the dimensional changes, while the changes are smaller than 0.5 mm. Gap L101 may produce an error between the rotation angles of rotor 1 and rotatable housing 14 engaged with steering shaft 15.